Characterization of physical and chemical properties of the envelope proteins of VSV, isolated and in situ; characterization of consequences of temperature-sensitive mutations causing lesions in either one of these proteins: measurements to be made using spin labelling, circular dichroism and fluorescence. Use of these mutants and isolated wild-type and mutant proteins to elucidate the initial events of viral attachment and entry into the host cell to initiate infection, and the final events of viral reorganization and budding from the host cell.